FAQ

How to use a liquefied petroleum gas (LPG) forklift properly—something you may not know!

　　During operation, to ensure proper use, liquefied petroleum gas (LPG) forklifts should adhere to the following guidelines:

　　1. First, familiarize yourself with the relevant manuals for LPG‑powered forklifts to gain a comprehensive understanding of the LPG conversion system. During operation, do not park the forklift near heat sources or ignition sources, such as open flames, burning cigarette butts, sparks, welding operations, or machinery and electrical equipment that can generate high temperatures. Do not attempt to adjust or modify the LPG conversion system yourself. Perform scheduled maintenance and inspections on a regular basis, remain vigilant, and address any leaks or abnormalities immediately.

　　2. Ensure proper startup: When operating a dual-fuel forklift on liquefied petroleum gas (LPG), verify that the manual valve on the cylinder is fully open before starting. If the forklift has been idle for an extended period, close the manual valve. Do not depress the accelerator pedal during startup. Set the switch to the LPG position, and after starting—especially in cold climates—it is advisable to warm up the engine for two to three minutes, allowing the coolant system to reach operating temperature before driving, thus ensuring that warm coolant can flow into the vaporizer to accelerate vaporization.

　　3. Pay attention to the fuel‑switching procedure (not applicable to single‑fuel forklifts): For dual‑fuel forklifts, switch only when the machine is fully stopped; never during operation. When switching from gasoline to LPG, keep the internal combustion engine idling, then turn the selector switch to the neutral position and allow any residual gasoline in the carburetor to burn out completely until the engine stalls. After that, move the fuel‑switching lever to the LPG position and restart the engine. When switching from LPG to gasoline, you can directly set the switch to the gasoline position without pausing at neutral; be sure to disconnect the pull‑cable. When the system is primarily running on LPG, maintain at least one quarter of a tank of gasoline as a reserve for emergencies. Additionally, periodically run the engine on gasoline to prevent the fuel system from failing due to prolonged inactivity and to avoid embrittlement of the fuel lines; it is recommended to burn approximately 10 kg of gasoline each month.

　　4. Perform refilling correctly: There are two methods for refilling—replacing the cylinder or directly charging it on the forklift. Refilling or replacing cylinders must be carried out outdoors, ensuring adequate ventilation and compliance with local fire‑safety regulations. The forklift must be securely parked and its engine turned off, and the operator must remain at the controls. Open flames, heat sources, and ignition sources are strictly prohibited in the vicinity. Handle cylinders with care; do not impact, drop, or roll them on the ground. During refilling, personnel must maintain continuous supervision and may not leave the site. To begin, attach the filling nozzle to the cylinder’s fill valve and tighten it securely, while also opening the 80% liquid‑level vent. Start refilling. If white vapor emerges from the 80% liquid‑level vent, immediately stop refilling, tightly close that vent, and verify that the liquid‑level indicator is accurate.

Diagnosis of Frost Formation on the Pressure-Reducing Valve of a K25 Single-Fuel LPG Engine

　　If, after installing a single-fuel LPG kit on the K25, the pressure-reducing valve No. 8 freezes, the following key factors may be responsible:

　　1. The antifreeze has not been filled to capacity.

　　2. If there are air bubbles in the antifreeze, they will accumulate at high points, including within the pressure‑relief valve’s coolant circuit; bleeding is required.

　　(Please refer to the method for filling with water and removing air bubbles in K25.)

　　3. Is the circulating water pipeline system unobstructed, and does the pipe diameter adequately ensure the required flow rate?

　　4. The water pipes are installed at an excessively high elevation, resulting in very low flow rates as the water circulates to the upper levels.

　　5. Is heavy-load operation performed immediately at idle or right after startup, causing the coolant temperature to remain low while the pressure‑relief valve cools the system excessively?

　　Especially in certain northern regions with cold winters, the forklift should be idled until the coolant reaches its normal operating temperature before commencing operation.

　　This is even more pronounced when the forklift is equipped with a heater.

　　6. The thermostat restricts water flow to a certain level and may freeze when exposed, preventing proper coolant circulation even after the engine has warmed up. You might consider removing this component.

Are you familiar with the issue of battery refurbishment for electric forklifts?

　　The applications of storage batteries are extremely broad, and battery‑powered products can now be found everywhere—for example, electric forklifts used in warehousing equipment. As usage time increases, the battery’s lifespan naturally declines. So, are you familiar with the issue of repairing electric forklift batteries?

　　It’s important to understand that not all damaged batteries can be repaired. For example, batteries that have sulfated due to deep discharging or insufficient charging during use can often be restored. For such sulfated batteries, simply applying a float‑charge mode with a charger that supports equalization is usually sufficient. However, batteries suffering from active material shedding on the plates, internal short circuits, or broken separators cannot be directly repaired—unless a qualified technician opens the case to inspect for detached plates, broken separators, or poorly soldered or missing connections, and replaces any defective components. Even then, this approach will do little to extend the battery’s service life. Non‑professionals should avoid disassembling or attempting to repair batteries on their own, as this could lead to skin and respiratory exposure, which, over time, may result in lead poisoning.

　　The so‑called high‑tech battery repair devices widely touted on the market simply cannot deliver on their promises. Electric forklifts rely on battery packs that are both bulky and heavy, and many users lack the knowledge to properly maintain and service these batteries. As a result, sulfation often occurs, impairing the electrochemical reactions on the battery plates and leading to short circuits and smoking in individual 2‑V cells. Once a 2‑V cell develops a short circuit, it must be replaced; even repeated charging and discharging cannot restore the faulty cell to balance with the rest of the pack. At this point, products marketed under the banner of cutting‑edge technology—such as certain battery repair devices—exploit the gap by claiming they can “revive” batteries. Lured by such miraculous claims, they then aggressively promote franchise opportunities, promising hefty profits. But if you fall for it… what happens next? The real motive is far from what it seems: their true aim is to rake in substantial franchise fees nationwide, while leaving you to invest your own capital and bear all financial risks yourself.

　　Battery repair has long been a topic of great concern for many users. We hope the points summarized by the editor at Shanghai Niuli Machinery will be helpful to you.

Different racking systems are paired with different forklifts.

　　Shelving systems can be customized to meet specific customer requirements, offering a variety of warehouse storage solutions, such as drive-in racking systems, very narrow aisle racking systems, double-deep racking systems, shuttle racking systems, gravity flow racking systems, push-back racking systems, and motorized mobile racking systems, among others.

　　Drive-in racking warehouse system

　　Standard forklift configuration for rack systems: a full‑depth rack system with no dedicated forklift aisles, where the forklift drives directly into the rack to store and retrieve goods.

　　Narrow-aisle racking warehouse system

　　Three-way stacker for rack systems: the guide rails typically use unequal‑leg angle steel, resulting in narrow aisles while retaining all the advantages of beam‑type racking.

　　Double-deep racking warehouse system

　　Rack‑mounted scissor‑type forklift configuration: The racks are designed with two parallel rows, allowing storage heights of up to 8 meters and achieving a 50% picking efficiency.

　　Shuttle Rack Warehouse System

　　Shelf‑based conventional forklift–shuttle system: Upon receiving instructions, the shuttle performs storage, retrieval, inventory counting, and other operations between the racks.

　　Gravity Rack Warehouse System

　　Shelf–standard forklift–roller track configuration: The forklift moves the goods to the higher end of the rack, where they slide down into storage under their own weight.

　　Push-back Rack Warehouse System

　　Shelving cart configuration: Multi-tiered carts are stacked and connected between the front and rear beams. Goods are placed on the carts from the outside and pushed in; as new items are stored, they push the previously stored goods toward the interior.

　　Electric Mobile Racking Warehouse System

　　Shelf‑motorized trolley configuration: A motor drives a load‑carrying trolley, which supports the shelving units. With variable‑frequency speed control, the system ensures exceptionally smooth operation from start-up to braking, providing reliable safety.

Common Fault Diagnosis and Troubleshooting for Difficult Diesel Engine Starting

　　 Causes of Diesel Engine Starting Difficulties

　　As dictated by the engine’s operating principle, the fuel system must inject fuel into the cylinder at prescribed intervals and in specified quantities, while ensuring proper atomization to facilitate efficient combustion. The performance of the fuel system is primarily reflected in injection timing, injection quantity, and atomization quality. If the fuel system malfunctions, it becomes difficult to maintain the correct timing, volume, and atomization of fuel delivery to the cylinder, thereby preventing the engine from starting. A common symptom is a smokeless exhaust—often indicating a lack of fuel—and no sign of ignition. The underlying causes can generally be attributed to the following factors:

　　(1) Causes related to the low-pressure fuel system (e.g., insufficient fuel supply)

　　1. The fuel tank is empty or contains insufficient fuel; fuel lines are cracked, allowing air to enter; connections are loose; water has entered the fuel; the fuel filter and relief valve are clogged; or the filter screen is blocked, among other issues.

　　2. The fuel tank valve is not open, or the air vent on the fuel tank cap is blocked;

　　3. Blockage in the pipeline between the fuel tank and the fuel injection pump;

　　4. There is an air leak in the pipeline between the fuel tank and the fuel transfer pump, allowing air to enter the fuel system.

　　5. Clogging of the diesel engine filter or the fuel transfer pump strainer;

　　6. The fuel injection pump relief valve is not sealing properly;

　　7. Water has entered the fuel system, or the wrong grade of diesel fuel is being used.

　　(2) Causes related to the high-pressure oil circuit:

　　1. Excessive wear of the fuel pump plunger–sleeve assembly results in significant internal leakage, preventing the fuel delivery rate from meeting the requirements during startup.

　　2. The fuel‑pump fuel‑delivery‑rate adjusting mechanism is seized, preventing the plunger from rotating or limiting its rotational travel to an insufficient degree.

　　3. The fuel outlet valve has a poor seal, resulting in no fuel delivery or insufficient fuel supply.

　　4. The injector needle valve is coked or sintered, preventing it from opening.

　　5. The opening pressure of the injector needle valve is set too high;

　　6. Injector nozzle blockage;

　　7. Air is present in the high-pressure oil line, or its fittings are loose.

　　8. Low injection pressure and poor fuel atomization, sticking of the needle valve in multi‑stage injectors, and breakage or damage to the injector adjusting spring, among other issues.

　　(3) Other reasons:

　　1. Incorrect fuel injection timing. Possible causes include wear of the pushrod roller and cam, damage to components of the fuel pump drive assembly, and improper adjustment.

　　2. The low-temperature starting preheating device has failed, resulting in excessively low cylinder temperatures in the diesel engine.

　　3. Fuel injection timing is too early or too late;

　　4. The cylinder compression pressure is too low, and the temperature and pressure at the end of compression fail to reach the level required to ignite the diesel fuel.

　　5. The cylinder fails to intake air, or the air intake is severely insufficient. Possible causes include a heavily clogged air filter, a blocked exhaust pipe, and excessively large valve clearances.

　　 Fault Diagnosis and Troubleshooting Methods

　　(1) Poor fuel supply in the low-pressure oil circuit.

　　In a diesel engine, the fuel supply and return lines between the fuel tank and the inlet chamber of the injection pump are all low-pressure circuits. When connections, gaskets, or fuel hoses in these lines leak due to damage, air can enter the fuel system, creating an air lock that impedes fuel flow, leading to difficulties starting the engine, sluggish acceleration, and other malfunctions; in severe cases, the engine may stall automatically. Additionally, if fuel lines age, deform, or become clogged with contaminants, reducing the effective flow area, or if dirty fuel blocks the inlet filter screen and the diesel fuel filter element, insufficient fuel delivery can result in reduced engine power and starting problems. To diagnose such faults, use the manual fuel pump to build up pressure, then loosen the bleed screw: if bubbles emerge and cannot be fully vented, it indicates air has entered the fuel system; if no bubbles appear but the diesel fuel discharged from the bleed screw flows weakly, it suggests the fuel circuit is blocked.

　　The method for troubleshooting is to identify and replace any damaged or aged gaskets, fittings, or fuel lines; to prevent such failures, regularly clean the fuel inlet strainer and diesel filter element, routinely inspect the fuel lines, and promptly address any issues that arise.

　　(2) The piston spring of the oil transfer pump has broken.

　　If the engine stalls suddenly while running and fails to restart, and after bleeding the air and restarting it resumes normal operation only to stall again after a short distance, the most likely cause is a broken piston spring in the fuel pump. To resolve this issue, simply unscrew the screw and replace the spring.

　　(3) The check valve of the oil transfer pump is not tightly sealed.

　　After the engine has been shut off and left stationary for a period, it may be difficult to restart. If you loosen the bleed screw, air bubbles will emerge, indicating that the air must be purged before the engine can start. This type of malfunction is often caused by an imperfect seal in the fuel pump’s check valve. To diagnose it, remove the fuel pump outlet screw and use the manual primer pump to fill the outlet‑connection oil chamber with fuel. If the oil level inside the connection drops rapidly within three minutes, this suggests poor sealing of the check valve. Disassemble the check valve and inspect the sealing surface for damage, check whether the spring is broken or deformed, and verify that no particulate contaminants are adhering to the seat. Address each issue accordingly—grind the sealing surface, replace the check valve, or replace the check valve spring—to resolve the problem.

　　(4) High-pressure oil line blockage.

　　When the high-pressure fuel line of a particular cylinder becomes blocked due to deformation or contamination, a distinct knocking sound will be heard at the fuel line after the engine is started, and the engine’s power output will drop because that cylinder cannot operate normally. To diagnose the issue, loosen the inlet nut of the high-pressure fuel line on each cylinder one by one; if the knocking sound disappears when you loosen the nut for a specific cylinder, that cylinder is identified as the faulty one. Replacing the fuel line will then resolve the problem.

　　(5) The injector nozzle pair is seized.

　　When the injector needle valve seizes in the closed position, pressure waves from the fuel pump can strike the injector, producing a regular knocking sound. To diagnose this, loosen the high-pressure fuel line connected to the injector; if the knocking sound immediately disappears, it confirms that the injector needle valve in that cylinder is seized.